1. Field of the Invention
The invention concerns an analytical element for the determination of an analyte containing in or on material which enables liquid transport between zones, a sample application zone and a detection zone located downstream thereof, wherein the detection zone contains a partner 1 of a specific binding pair 1 immobilized in such a manner that it is able to bind with partner 2 of the specific binding pair 1 which is not the analyte when this contacts it as well as a method for the determination of an analyte by means of specific binding pairs. The invention additionally concerns a kit for the determination of an analyte containing an analytical element.
2. Description of Related Art
Analytical elements are known from the prior art in which the reagents required to determine an analyte are present in or on carrier materials. Examples are: U.S. Pat. No. 4,861,711, U.S. Pat. No. 5,591,645 and EP-A-0 291 194. A common feature of the analytical elements described in these documents is that they are especially suitable for carrying out immunological detection methods. They comprise a sample application zone and a detection zone which is located downstream thereof. A liquid sample migrates through various zones between the sample application zone and detection zone as a result of capillary forces within a porous carrier material and thereby takes up the reagents that are necessary for detecting the analyte and reacts them with the analyte in the sample.
A binding partner is immobilized in the detection zone which is able to specifically bind the analyte to be determined. In the case of different analytes this requires that different binding partners for the analyte have to be immobilized on a solid phase.
It is also known from FIG. 1 of U.S. Pat. No. 4,861,711 in conjunction with the description, for example in column 5, line 57 to column 6 line 48 that a partner 1 of a specific binding pair 1 can be immobilized in the detection zone which does not bind the analyte but can be used universally because it binds an epitope as partner 2 of the specific binding pair 1 which is present on a substance which specifically binds the analyte. Hence the mobile complex of analyte and this binding substance is immobilized in the detection zone during the course of the detection reaction and is separated from non-complexed mobile reaction components.
A labelled substance that is specific for the analyte plays a very important role because only its binding to the analyte and the later immobilization of the complex formed composed of analyte and labelled substance directed against the analyte in the detection zone as well as the removal of the mobile non-reacted reaction components from the detection zone is able to indicate the presence of analyte in the liquid sample. The labelled substances known from the prior art are specific for the analyte i.e. in the case of sandwich assays they are labelled substances such as antibodies or antigens which react specifically with the analyte to be determined (antigen or antibody). However, this requires that depending on the analyte, different labelled specific binding partners for the analyte have to be prepared.
Numerous substances are known from the prior art for labelling. Whereas in the past radioactive labels with all their disadvantages were used, these labels were later replaced mainly by enzyme labels. Nowadays particulate labels, especially gold or latex particles, are mainly used in analytical elements as described in the previously described documents of the prior art. The preparation of a conjugate composed of a label and a substance binding specifically to the analyte is complicated and has to be optimized for each individual analyte-specific binding partner if it is intended to determine different analytes. In addition in analytical elements the material on which this conjugate is present and transported must be optimally adapted to the requirements from case to case. In this connection above all stability problems have often to be solved.
Therefore the object of the present invention was to provide a general purpose structure of an analytical element which can always be used independent of the analyte to be determined provided this analyte or a substance derived from the analyte and representing this analyte can be detected by specific pair binding.